2
3.0 Installation
Installation of both the drive-by-wire throttle bodies and pedal assembly should be performed by a professional, competent mechanic. It
is important that the installation of both the throttle bodies and pedal assembly on an engine (not originally equipped with these
components) be done in such a manner that assures proper operation of both components as intended by the OEM manufacturer.
The throttle bodies must be installed in such a manner that the throttle plate(s) are allowed to rotate freely.
The pedal assembly must also be installed in such a manner that it is rigidly and securely mounted, yet does not put the pedal
in a bind, or put any mechanical stress on the electrical and electronic components. Proper positioning of the pedal is of the
utmost importance.
The accelerator pedal must have adequate clearance throughout the range of its travel to prevent the possibility of the pedal
coming in contact with any item that may cause it not to return to the “idle” position upon release. The accelerator pedal must
also be mounted far enough away from the brake pedal as to allow for the vehicle’s brakes to be fully applied without the
operator’s foot coming in contact with the D-B-W pedal.
The drive-by-wire pedal should be in a position such that it is lower than the brake pedal when the brake pedal is depressed.
Installation of the wiring harness supplied by Holley must be done so that there is no chance the wiring may be cut or abraded.
Rubber grommets should be utilized wherever the harness passes thru a firewall / sheet metal panel.
The DBW harness should never be routed in such a manner that it may come in contact with “noisy” electrical components or
wiring that may emit RFI and/or EMI noise. Typical “noisy” components and associated wiring in a vehicle would be spark plug
wires, ignition coils, high energy ignition boxes, two-way radios (including CB’s), etc. Maintain a minimum of 5” of clearance to
any of these types of components.
The harness is designed to be “plug-and-play” with the throttle bodies and pedal assembly indicated above. It should not be used for
any other applications.
4.0 System Safeties
Holley designed the drive-by-wire system to utilize a brake pedal switch input. This is wired to a +12v input from the brake pedal
switch. If the brake pedal is depressed enough to activate the brake light switch, the following occurs:
The ECU will not allow a pedal position over 10%, no matter how far the pedal is pushed. This consequently limits the
opening of the throttle bodies.
Before a pedal value over 10% will be recognized, the following must occur in this order:
Brake pedal switch must be released
Pedal position must go below 10%
Fuel flow is limited to 30 lb/hr as an additional safety.
IMPORTANT! INSTALLATION OF THIS SAFETY CIRCUIT IS REQUIRED WHEN USING THE DRIVE-BY-WIRE FEATURE!
DEFEATING OR NEGLECTING TO INSTALL THIS INPUT IS DONE SO AT THE USERS OWN RISK. THE USER
ASSUMES ANY AND ALL LIABILITY FOR ANY DAMAGE, AS A RESULT OF A DRIVE-BY-WIRE MALFUNCTION.
Most drive-by-wire systems are designed so there are two position sensors on both the throttle body and the accelerator pedal
assembly. This is done as a failsafe in the event that one of the position sensors should fail. Holley EFI systems require that both sets
of sensors are functioning 100% properly. If any sensor moves from its calibrated position, the throttle body is immediately de-
powered, forcing it to move to the factory “limp home” position. The “limp home” position is described in detail below. Whenever a fault
is detected and the throttle body is de-powered, a fuel flow limit of 30 lb/hr is also introduced.
5.0 Throttle Body “Limp Home” Position
Factory Drive-By-Wire Throttle Bodies have a “Limp Home” position. This is the position that the throttle body is at when no power is
applied. It is typically enough air flow to allow a car to move at a speed of approximately 45 mph. This varies by manufacturer, but is
the case with the GM throttle bodies this harness supports. However, when two throttle bodies are used, the speed may be noticeably
higher.
It should be strongly noted that this position allows MORE airflow than the engine uses for an idle position. If the throttle body goes into
a “limp home” position due to a sensor failure or other reason, the engine will have more air and result in more power. This will require
more brake pressure to be applied if a vehicle is in gear so that it does not move.